Press machines such as punch presses commonly use, as a press driving source that moves press tools forward and backward, a mechanism that converts rotary motion of rotary electric motors into rectilinear motion via a crank mechanism, or a hydraulic cylinder. Proposal has also been made of press machines using servo motors as electric motors to vary punch speed during strokes (for example, the Unexamined Japanese Patent Application Publication (Tokkai-Hei 8-1384)). However, press machines using rotary electric motors require a mechanism that converts rotary motion into rectilinear motion and thus have complicated configurations. Further, since rotary motion is converted into rectilinear motion, lost motion or the like may occur, degrading controllability. Press machines using a hydraulic cylinder require a hydraulic supply system such as a hydraulic unit and thus have complicated structures.
Attempts have also been made to use linear motors as a press driving source. Where used to drive punches, linear motors, unlike rotary motors, eliminate the use of a mechanism that converts rotations into rectilinear motion. The linear motor thus reduces the number of parts required and simplifies the structure.
Press working by a punch press or the like generally requires the use of the same machine for different machining operations including one needing a greater press tonnage and one needing only a smaller press tonnage. Where the same linear motor is used to perform these machining operations with markedly different press tonnage, a high-power linear motor is used. However, the high-power linear motor is large and has a heavy movable portion, making it difficult to achieve high-speed operations. Further, even if high-speed operations can be achieved, the high-power linear motor involves increased power consumption, preventing efficient operations. Further, the high-power motor may not be preferable in connection with possible vibration during high-speed machining. Thus, it is not practical to use the high-power linear motor for applications requiring high-speed machining.
Furthermore, linear motors generally use permanent magnets with a strong magnetic force. However, it is difficult to manufacture motors each providing a high thrust owing to the manufacturing limit on the size of magnets, limitations on supply voltage, or the like. Press working may require a linear motor that can produce a thrust higher than that required for general machining. Thus, a required press tonnage may not be provided by a single linear motor. Thus, only some of a plurality of coupled linear motors may be driven for machining with a small press tonnage. However, in this case, the coupled linear motors in a non-driving state may act as resistance to reduce the efficiency of use of electric energy.
It is an object of the present invention to provide a linear motor mounted press machine which has a press driving source of a simple configuration comprising linear motors and which can generate an optimum thrust for a press tonnage to perform different machining operations including one requiring a greater press tonnage and one requiring a high speed and a smaller press tonnage in an energy efficient manner.
It is another object of the present invention to use a plurality of linear motors to increase power, while providing balanced rectilinear-propagation outputs and to allow a thrust of a small press tonnage to be efficiently produced when machining is performed using only a second linear motor.
It is yet another object of the present invention to spatially efficiently arrange the linear motors to obtain a further compact configuration.
It is still another object of the present invention to allow each of the linear motors to be made compact and efficient and to enable the unit linear motors to be combined into a simple configuration.
It is further another object of the present invention to appropriately drive both linear motors to efficiently perform a machining operation requiring a greater press tonnage and a machining operation requiring a high speed and a smaller press tonnage.
It is further another object of the present invention to allow energy-efficient machining corresponding to the press tonnage to be performed by simple control.
A linear motor mounted press machine in accordance with the present invention comprises a first linear motor, a second linear motor that produces a thrust lower than or equivalent to that of the first linear motor, a coupling switching mechanism that releasably couples output shafts of the first linear motor and the second linear motor together, and a press tool that is driven forward and backward by the output shaft of the second linear motor.
This configuration moves the press tool forward and backward using the linear motors, eliminating the need for a mechanism that converts rotation into rectilinear motion, as opposed to configurations using rotary motors. This provides a simple structure with a reduced number of parts. The press machine also comprises the first linear motor and the second linear motor, and the coupling switching mechanism coupling these linear motors together. Thus, for machining requiring a greater press tonnage, both linear motors are coupled together and driven, or the first linear motor, which produces higher power, is driven to enable machining corresponding to the required greater press tonnage. For machining requiring only a smaller press tonnage, the coupling switching mechanism is brought into a decoupling state to allow only the second linear motor, which produces lower power, to be used for driving. This enables high-speed machining with reduced vibration. In this case, the first linear motor is disconnected from the second linear motor and thus does not resist the driving of the second linear motor. This enables efficient operations.
In the present invention, each of the first and second linear motors may be a unit linear motor assembly having a plurality of unit linear motors arranged around a press working axis center along which the press tool elevates and lowers, and the second linear motor may have fewer unit linear motors than the first linear motor. When each of the first and second linear motors is the unit linear motor assembly, the power of the individual unit linear motors can be collectively used to obtain high power. Further, the plurality of unit linear motors are arranged around the press working axis center. Consequently, balanced rectilinear-propagation outputs can be obtained in spite of the installation of the plurality of unit linear motors. The second linear motor has the fewer unit linear motors than the first linear motor. This reduces the mass of the operative portion. When only the second linear motor is used for machining, a thrust of a smaller press tonnage can be efficiently produced.
When each of the first and second linear motors is the unit linear motor assembly, the second unit linear motors may be arranged inside an arrangement of the unit linear motors of the first linear motor. Thus, the arrangements of the unit linear motors of the first and second linear motors are concentric and form a double arrangement, making it possible to make the entire arrangement compact. In this case, the second linear motor for a smaller press tonnage is located inside. This enables a spatially efficient arrangement corresponding to the size of each of the linear motors. Therefore, an efficient, more compact arrangement can be achieved.
In the present invention, the unit linear motor may be a cylindrical linear motor having a shaft member comprising a permanent magnet having N poles and S poles alternately arranged in an axial direction and a coil unit through which the shaft member is movable relative to the coil unit. In the cylindrical linear motor, the coil unit is positioned around the periphery of the magnet member, allowing magnetic fields to be efficiently utilized. This linear motor is thus compact and efficient.
In the present invention, the press machine may further comprise a coupling state and motor-to-be-used selection control means for performing control such that when a required press tonnage is smaller than a set press tonnage, the coupling switching mechanism is brought into a decoupling state to allow only the linear motor to be driven, and when the required press tonnage is at least the set press tonnage, the coupling switching mechanism is brought into a coupling state so that the first press driving source cooperates with the second press driving source in performing a driving operation. Where the coupling state and motor-to-be-used selection control means is provided to control the coupling and driving of both linear motors in accordance with the required press tonnage, both linear motors can be appropriately driven to efficiently perform a machining operation requiring a greater press tonnage and a machining operation requiring a high speed and a smaller press tonnage.
In the present invention, where the first or second linear motor comprises a plurality of unit linear motors, the press machine may further comprise a unit linear motor selection control means for selectively driving some of the plurality of unit linear motors of one of the first and second linear motors. Driving only some of the unit linear motors allows machining to be performed in accordance with the press tonnage in an energy efficient manner.
The linear motor mounted press machine in accordance with the present invention comprises the first linear motor, the second linear motor that produces a thrust lower than or equivalent to that of the first linear motor, the coupling switching mechanism that releasably couples the output shafts of the first and second linear motor together, and the press tool that is driven forward and backward by the output shaft of the second linear motor. Thus, the press driving source has a simple configuration comprising the linear motors. Further, the optimum thrust for the press tonnage is generated to enable different machining operations including one requiring a greater press tonnage and one requiring a high speed and a smaller press tonnage in an energy efficient manner.
Each of the first and second linear motors is the unit linear motor assembly having the plurality of unit linear motors arranged around the press working axis center along which the press tool elevates and lowers. Further, the plurality of unit linear motors provide balanced rectilinear-propagation outputs. Where only the second linear motor is used for machining, a thrust of a smaller press tonnage can be efficiently produced.
When each of the first and second linear motors is the unit linear motor assembly, where the second unit linear motors are arranged inside the arrangement of the unit linear motors of the first linear motor, then the linear motors can be more spatially efficiently arranged, resulting in a more impact configuration.
When the unit linear motor is the cylindrical linear motor having the shaft member comprising the permanent magnet having N poles and S poles alternately arranged in the axial direction and the coil unit through which the shaft member is movable relative to the coil unit, each unit linear motor may be compact and efficient. Further, the plurality of unit linear motors can be combined into a simple configuration.
In the present invention, where the press machine further comprises the coupling state and motor-to-be-used selection control means for performing control such that where the required press tonnage is smaller than the set press tonnage, the coupling switching mechanism is brought into the decoupling state to allow only the second linear motor to be driven, and when the required press tonnage is at least the set press tonnage, the coupling switching mechanism is brought into the coupling state so that the first linear motor cooperates with the second linear motor in performing a driving operation, both linear motors can be appropriately driven to efficiently perform a machining operation requiring a greater press tonnage and a machining operation requiring a high speed and a smaller press tonnage.
In the present invention, where the press machine further comprises the unit linear motor selection control means for selectively driving some of the plurality of unit linear motors of one of the first and second linear motors, energy-efficient machining corresponding to the press tonnage can be performed by simple control.
Other features, elements, processes, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments of the present invention with reference to the attached drawings.